Machine for computing interest



(No Model.)

J. W. ROBINSON.

MACHINE FOR COMPUTING INTEREST.

NM Q Mw l ,UNITED ST1-tras @PATENT J.`\VATTS BOBNSON, OF BOSTON,MASSACHUSETTS.

MACHiNE Fea confiseries intenser.

SPECEFICATION forming part of Letters Patent No. 294,079, dated February2G, 1884.

Application filed December 15,1333.

T0 @ZZ whom, it may concern:

Be it known that l, J. WATTS Ronrrson, of Boston, in the county ofSuffolk and state of Massachusetts, have invented a ceitaiii new anduseful Improvement in Machines for Computing Interest, AveragingAccounts, 85e., of which the followingisadescription,suciently full,clear, and exact to enable any person skilled in the art or science towhich said invention appertains to make and use the same, referencebeing had to the accompanying drawings, forming a part of thisspecilication, in which- Figure l is a vertical transverse section takenon line x in Fig. 2, Fig. 2, a top plan view, and Fig. 3 aV verticallongitudinal section taken on line z in Fig. 2.

Like letters of reference indicate corresponding parts in the differentfigures of the drawings.

My invention relates to a means for computing interest, averagingaccounts,'&c.,: and it consists in a novel construction and arrangementof the parts, as hereinafter more fully set forth and claimed, by whicha more effective device of its character is produced than is now inordinary use.

The nature and operation of the improvement will be readily understoodby all conversant with suoli matters from the following explanation:

In the drawings, A represents the bodyof the machine; B, the carriage,and C the slide.

The body consists of an elongated box, coinposed of tin or any othersuitable material, open at the top, and having the sidesf, bottom o, andends g. Abraeket, Z, projects from one side of the body, and extends itsentire length, asbest seen in Fig. 2. y

The carriage Bis adapted to slide longitudinally on the body A, beingprovided with two downwardlyprojecting lips or flanges, m., one

i of which works in the groove t, between the side of the body and thebracket Z, the other overhanging the opposite side of the body, as bestseen in Fig. il.

The slide C is mounted on the carriage B, and adapted to movetransversely thereon, or at right angles to the line z, being supportedand secured on the ways p, which project upwardly from the carriage.rllhe carriage is provided on its upper side with a scale or col- (Nomodel.)

umn of iigures, E, in numerical order, from t) to 36, arranged inparallelism to the line the slide C being provided with a correspondingslot, a, through which the scale may be seen. In the drawings a portionof the scale, or Vfrom 0 to 3, is represented as covered by the slide C.The slide C is also provided with a scale or column of figures, D, innumerical order, from O to 33, arranged at one side ot' the slot a, andin parallelism therewith, the two scales D E being brought into properpositions in respect to each other by moving the slide C back and forthon the carriage B in using the machine.

rlhe bracket lis provided with a scale, F, which has the names(abbreviated) of all the months running through two yea-rs, togetherwith -two series of iigurcs, the iigures ot' one series being largerthan those ot the other, as seen in the drawings, to some of whichlarger figures is preiixed a dash or niinussign. The carriage B isprovided with a similar scale, G, consisting of the abbreviated names ofmonths, of larger and smaller iigures, and of a star, (ij) the months onthis scale extending through only a single year. The scale G is employedin varying combinations with the. scale F in using the machine,

A portion of the body L serves as a receptacle to hold and store tabiesof interest-com` putations, peculiariy arranged at the various rates percent. called for, a section of one of which tables (marked H) appears inthe drawings in position for use. rihese tables of interest are ofuniform size, and are held in position by the sides j' f of the body A.,and by abutting against other tables ofngures placed in the otherreceptacle or opposite end of the body d. The table which relates to therate of interest desired is placed at the top of the pile ot tables inthe left-hand receptacle, and is replaced by others, as occasionrequires. The right-hand portion of the body A serves as a receptaclefor another series of tables of interest, similar to those in theleft-hand rcceptacle, and also for a table ot' figures running ironi lto 365, peculiarly arranged, as hereinafter explained, the iiguresthereon representing days. A portion ot' this last-nientioned tableappears in the drawings, and is4 convenience in moving the slide, andalso the carriage B, or either, as desired. The slide G is provided onits sides with laterally-projecting iianges T U of peculiar and suitableshapes, as shown in Fig. 2 of the drawings, the flange T being providedwith the square end M and shoulder N, and the ange U with the end P andshoulder R, these being used to indicate the interest or days,asexplained in the examples hereinafter given.

The object of the machine is,iirst, to show mechanically, and in a readyand simple manner, the interest on one dollar at any rate per cent., andfor a period between any two dates within a year of each other, usingeither three hundred and sixty or three hundred and sixty- -flve days tothe year basis, and counting either thirty days to the month or theactual number of days between the dates, and without computing or evennecessarily knowing the length of time; secondly,'to show the interestat any rate per cent. on the same amount,with

outiregard to dates, for any number of months of thirty days each, plusthe odd days, or for the actualv number of days, with but little or nocomputation, as will be shown in the accompanying examples; thirdly, toshow the interest on any number of dollars less than v three hundred andsixty-five, or on multiples of any number of dollars less than threehundred and sixty-six, by ten, one hundred, one thousand, or tenthousand-as, for example, $275, $2,750, $27,500, $275,000, or$2,750,000-

without any computation whatever; fourthly,v

to ascertain mechanically, in a simple and ready manner, for any purposewhatever, the time either in months of thirty dz ys each, plus days, orin actual numberof days between any two dates. v

The machine may be made to show interest at any two desired rates percent., simultaneously and by the same' operation, by placing one of therates 011 top in the left-hand receptacle or end of the body, and theother on the top in the right-hand receptacle or end of the body, or toshow interest at any one rate, and also the length of time betweendates, simultaneously and by same operation, by arranging the tables soas to show the table of interest on top at the left and the table ofdays on top on the right of the body A.

The operation is as followsQ First, to show, simultaneously and by thesame mechanical operation, the interest on one dollar between any twodates, (counting each calendar-month as thirty days, or the twelfth partof a year, and each of the odd days as the three-hundred-and-sixtiethpart of a year,) and also the time between the same two dates, (countingtime in same manner,) place the table of interest at the required rateon the top of the other tables in the left-hand receptacle and the tableof days on top in the right-hand. receptacle, as represented in Fig. 2of the drawings. Then move scale G so that the month of the iirst datethereon vshall be directly below the month of last on scale E, and theiigures representing the interest will be seen directly above the end Mor below the shoulder N of the ange T; or at both of these points.(There'can be no mistake made in referring to these points, for wherevergures appear at both points at the same time the figures so appearingwill be exactly alike.) By the same operation the number of days,counting time in the same manner, between the dates will be seendirectly above end P or below shoulder It, or at both points, of theflange U.

Secondly, if interest is to be shown for the actual number of days fromdate to date, ex-

actly the same process is performed, but afterward the slide C is moveddown or up a distance equal to that of a number oi" spaces on the scaleE equal to the positive or negative sum, respectively, of the two largenumbers situated on scales F and G, and between the first and lastmonths between which interest or time is desired. If the sum of thesetwo numbers be `a minus quantity, the slide C is moved up as many spacesas there are units in this sum, and itl the sum be a plus quantity theslide Gis moved down as many more spaces as there are units in the sum,(or, the sum of the two numbers on scales F and G, as just mentioned,may be added to or subtracted from the last date, according as this sumis a plus or minus quantity,) andthe first date on scale D be broughtydirectly opposite thisl increased date or scale E. In either case theinterest or time will be shown,as explained above.

Example: To show interest on one dollar at six per eent.,'(this tablebeing represented in drawings as being on top and marked H,) from March4 to June 7, (thirty days to the month,) move the carriage B so thatMar. on scale G will be directly below Jun. on scale F, and move slide Cso that 4 on scale D will be exactly opposite 7 on scale E, and theiigures 1.5500 immediately either above` IOO the end M or below theshoulder N of the slide C, represent the interest required, in cents anddecimals thereof, for the time given, as shown in Fig. 2 of thedrawings. At the same time the figures 93, immediately above the end Porbelow shoulder R of the ilange U, represent the number of days betweenabove dates, counting each calendar-month as thirty days. If interestfor the actual number of days (each day being counted as the threehundred-and-sixtieth part of a year) or time (on the same basis) isrequired, move the slide C down two spaces more, (equal to the sum ofthelarge figures l and 1, situated on scales FandGand between Man andJnn.,) and the interest will be shown at the points M and N, and thetime (actual days) at the pointsl? and R. By substituting a tablecalculated on the basis of three hundred and sixty-ve days to the yearfor the one calculated at three hun- .dred and sixty days to the year,interest for the actual number or" days from one date to another on thisbasis may be obtained in a similar manner. To iind interest onninety-three dollars for one day, move the carriage B and slide C sothat theshoulder P will be `directly below or the end R directly abovethe gures 93 on the right-hand table, Las shown in Fig. 2 ofthedrawings, and the interest will be indicated both above the end M andbelow the shoulder N to be 1.5500 cents. For nine hundred and thirtydollarsit would of ceu rse be 15. 500 cents. For nine thousand threehundred dollars, 155.00 cents, and so on by simply changing the positionof the decimal point; andthe same rule will hold for all amounts ofdollars less than three hundred and sixty-six dollars or multiples ofany ofthcm byten, one hundred, &c. By substituting for the table of days(now on the rightin Fig. 2) any one of the-tables ofinterest, either onthe basis of three hundred and sixty or three hundred and sixty-fivedays to the year, interest will be shown in the same manner at two ratessimultaneously by one and the same mechanical operation. In caseinterestis required to be shown at only one rate at a time, and the table ofdays is on top at the right, (as now represented in Fig. 2 ofthedrawings,`) the shoulder F is brought directly below the given number ofdays on t-he table of days J, and the interest on one dollar'will beshown directly above the end M. So, in like manner, if the interest isrequired for ninety-three days, bring the shoulderF (where it isrepresented) below 93, and the interest will be shown at M. To showinterest for any number of months of thirty days,plus the odd days,disregarding dates, b ring the star (it) on scale G directly under thesmall figure which represents on scale F the number of months, and thezero (0) on slide D opposite the number oi' odd days on scale E and theinterest is shown ,as before explained. For instance, tal;- ing themachine as represented in Fig. 2 of the drawings, the interest for threemonths .and three days is shown, the star on scale G being` below thesmall figure 3 on scale F, and the zero (0)011 scale D exactly opposite3 of scale E, as it would be arranged for interest at that time. Vheninterest is required for a longer time than one year, by adding to theunit-iigurc of the interest, as shown on tables for the time, (notcountingv the whole years,) a number equal to the rate per cent.multiplied by the number of whole years between the dates, and anncxingthe decimal part, the interest is obtained on one dollar for the time,or between the dates, without regard to time, abstractedly, or itslength between the dates. For example, when the machine is adjusted asrepresented in the drawings, to iind interest on one dollar from March4,1880 ,tc J une 7 1883, it has already been found that the interestfrom March et to June 7 of any year on the "the unit-figure of thelatter.

1880, to J une 7, 1883. 'In the same manner, by adding to the number ordays contained in the odd months and days, or in the time between thefirst and. last dates, as the case may be, (disregarding the wholeyears) a number equal to three hundred and sixty-iiye multiplied by t-henumber of the whole years, and it will give the actual number of daysfor the time, or between the dates; but for each time February 29 ispassed one more unit must be added. When February 29 comes between thedates, or within the time, the slide C ismoved down so that the iirstdate on the scale D will be opposite the number on scale E, which is onegreater than it otherwise would be.

rIhe utility and value of the machine as au aid in computing interest onany amounts at any rate for any length of time, and on any basis ofcaleulatien,is demonstrated by the fact that whenever the interest onone dollar is eertained the interest on any required amount may bereadily determined. Of course, the interest on one dollar beingexpressed (as it is in the tables) in cents and decimals oia cent, it isonly necessary to multiply this interest by the dollars of the principalin the ordinary way, and the interest on the whole amount will be shown,but the process may be short- 9 ened and the number ot' iigurcs in thecalculation very much lessened with equal accuracy by proceeding asfollows: Use t-he interest as the multiplier, but place its iigures ininverse order under the multiplieand, (principah) t-he unit-iigure ofthe former being directly under Then multiply each igure of themultiplier into the gures above andto the left of it, as in ordinarymultiplication; but place the right-hand figure of each partial productdirectly under the righthand iigure of the multipler, and place theothers to the left in succession, as usual. For exactness, although itis not necessary to make use of the whole product of any figure ofthemultiplier by any iigure standing on its right in lthe multiplicand, thetens-tigure of such product (increased by one if its unit-figure is tiveor greater) should nevertheless be carried to the product ofthe twoiigures, which stand under and above each other.

1n order to exemplify the abeve,1 give the following two examples, whichwill explain the difference between the facility of using what 1denominate the long way and the short way:77

Long Way. Short Way.

In both of these examples the principal is $573 and the interest on S1is L.286 cents. The

IOO

IIO

IZO

ti ures representing interest are used, under the heading short way,77as multiplier, but are reversed, as seen, and the whole 573 ismultiplied by the 4, the product being 2292. The 57 is multiplied by the2, carrying l vfor the 6 units (carried. as one ten from multiplying the3: by 2) making 115. The 5 is multiplied .by the S (carrying 6 from theproduct of the S by 7) making 46, and 3 is carried from the product of 6multiplied by 5 (there being no figure above the 6,)'making 3,. whichpartial products are added, as seen in the example under heading shortway, the result being $524.56, or the same as by the long Way,77 butproduced' with much fewer ngures and in less time. It will also be seenthat it is necessary to use only as many of the decimal iigures of theinterest as there arev places of gures in the principal.

The ilangesU T are widest at the shoulders P N, or so constructed as tocover two columns or figures on the tables at that point, the ends R Mbeing narrow or covering but one column, this form facilitatingtheworking of the n1achine, as the correct' figures are thereby morereadily ascertained.

I do not, confine myself to using the scale G on the carriage only, asit may be mounted 4 :reacts on the slide and perform substantially thesame functions.

Having thus explained my invention, what I claim i'sl. In a device forcomputing` interest, substantially such as described, the body A,pr'ovidedwith the tables II .I and scale F, the car- 35. I

riage B, provided with the scales E G, and the slide G, provided withthe slot a, scale D, and flanges 'I U, combined and arranged to open atesubstantially as set forth. A

2. In a device for computing interest, sub- 4o stantially such asdescribed, the body A, provided With the bracket Z for the scale F; andwith the groovet for receiving the flange m of thecarriage B, and-thereby preventing the Vcarriage from moving longitudinally, subsian- 45

